This invention relates to aqua-ammonia absorption cooling and/or heating systems utilizing ammonia refrigerant and aqueous absorbents. Improvements in the efficiencies of such systems include the use of generator/absorber heat exchange cycles utilizing rich and weak absorption working fluids and/or by separate heat exchange loops referred to as GAX cycles. Descriptions of such systems are found in U.S. Pat. Nos. 4,311,019, 5,024,063, 5,271,235, 5,367,884, Re. 36,684 and R. J. Modahl and F. C. Hayes, xe2x80x9cEvaluation of Commercial Advanced Absorption Heat Pump Bread Board,xe2x80x9d The Trane Company, pp. 117-125, 1988. Additional improvements are described in co-pending U.S. patent application Ser. Nos. 479,277, filed Jan, 5, 2000 (ROCKYR.099A); 632,037, filed Aug. 3, 2000 (ROCKYR.105A); 632,054, filed Aug. 3, 2000 (ROCKYR.106A); and 709,875, filed Nov. 10, 2000 (ROCKYR.103A). The description of the aforesaid patents and applications are incorporated herein by reference.
Most operating hours during which the aforesaid systems are used typically occur at ambient temperatures where the load is less than the design building load, and less than the design capacity of the system or appliance. The aforesaid aqua-ammonia absorption systems or appliances incorporate single-speed burners or burners having a single firing rate. The usual means for providing heating and/or cooling at part load conditions is to cycle the appliance on and off. However, such systems experience cycle losses which decrease efficiency when they are so operated. Also, startup delays reduce desired heating or cooling response times with resulting inconsistent or non-uniform temperature controls. Single speed operation also does not take full advantage of the ability of the system to operate more efficiently at lower ambient temperatures, and takes no advantage of the capability of a system to operate more efficiently at part load.
As described herein, an aqua-ammonia absorption cooling and/or heating system incorporates a variable speed or multiple speed bumer, a burner having a continuously variable burner speed or firing rate, or a burner having a plurality of discrete burner speeds or firing rates. The terms burner speed and firing rates variable speed, multiple speed, and variable firing rate are used interchangeably herein as are the terms and, unless otherwise indicated variable or multiple speed, cover either continuous or discrete burner speeds or firing rates.
In one embodiment, a variable speed burner is used in combination with active control of weak liquor flow from the generator to the absorber assembly. Weak liquor flow is controlled in response to temperature, and/or pressure and/or concentration of the weak liquor. In another embodiment, weak liquor flow is actively controlled in discrete steps in response to burner speed.
In another embodiment, in an aqua-ammonia heating and/or cooling system, a variable speed burner is used in combination with active control of the flow of rerigerant to the system evaporator.
In another embodiment, a variable speed burner is used in combination with both active control of weak liquor flow and active refrigerant flow control.